The exemplary embodiments relate generally to a fuser system of a xerographic device and a method of fusing an image in a xerographic device, which includes a closed loop control of the user system based on the torque applied thereto.
In the process of xerography, a light image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a photosensitive member with subsequent rendering of the latent image visible by the application of particulate thermoplastic material, commonly referred to as toner. The visual toner image can be either fixed directly upon the photosensitive member or transferred from the member to another support, such as a sheet of plain paper, with subsequent affixing of the image thereto, one method of affixing including the application of heat and pressure.
In order to affix or fuse toner material onto a support member by heat and pressure, it is necessary to elevate the temperature of the toner and simultaneously apply pressure sufficient to cause the constituents of the toner to become tacky and coalesce. In both the xerographic as well as the electrographic recording arts, the use of thermal energy for fixing toner images onto a support member is known.
One approach to heat and pressure fusing of toner images onto a support has been to pass the support with the toner images thereon between a pair of pressure engaged roller members, at least one of which is internally heated. For example, the support may pass between a fuser roller and a pressure roller. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the fuser roll thereby to effect heating of the toner images within the nip.
However, when the pair of pressure engaged roller members, at least one of which is internally heated, are not at an adequate temperature, such as, for example, when the xerographic device has not yet warned up, the torque reflected to the motor may be too high. That is, the torque required to rotate the loaded roll pair decreases as the temperature of roller members increases. The motor power may not be sufficient to drive the pair of rollers when the rollers are “cold.” However, the load motor will continue to drive the roller members until the appropriate engaged position is achieved. This may lead to a motor stall, or other inefficiencies.